Mechanic can't find a rear end!

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Mechanic can't find a rear end!

Postby kgkoon » Wed Oct 03, 2012 3:00 pm

Hey guys, I've got a problem with my 2003 ZR5. The rear end went out back in 2007 and I had it replaced. It just went out again two weeks ago and I took it to a different mechanic.

The new mechanic says the old mechanic installed a ZR2 rear end and it was wrong. He couldn't believe it lasted 5 years.

The new mechanic has been looking for the correct rear end. He has ordered THREE so far only to find out when they arrived they were wrong. The last time I talked to him he claimed they were having a very difficult time finding the right one. He was saying something about the sizes not matching and they keep sending him ZR2 rear ends.

Does any of this make sense? What are my options? I only need this truck as a commuter. I don't need the 4wd, I just need it to drive from point A to point B.

Thanks for any help you can give me.
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Re: Mechanic can't find a rear end!

Postby HenryJ » Wed Oct 03, 2012 4:41 pm

I assume that you mechanic is trying to replace the differential assembly and not the complete rear axle assembly.
The stock differential uses a 7.625" ring gear diameter. This is referred to as a 7.625" or 7 5/8" differential.
The ZR2 had a 8.5" ring gear and is called the 8.5" or 8 1/2" differential.
The housing for each of these is different due to the size of the ring gear.

If you have a 3.73:1 gear ratio, I would suggest you bite the bullet and install a complete rear axle assembly from a ZR2. The 8.5 rear axle is a substantial upgrade and well worth the investment. You may need to use an adapter u-joint in some cases. Mine was a direct bolt in swap. The 3.73 ratio was a common one for the ZR2 and easy to find. There are several good threads on this swap.

If you have the 3.42:1 gear ratio, I suspect you will continue to search for a suitable replacement differential assembly. Be warned that the sift pinion shims and axle side gears on the open differentials , may continue to plague you in the future. Use a G80 Eaton GovLoc differential if possible. Those were more common in the optional offroad package and 3.73 gear ratio.

Car-part.com is a good place to search used inventory for parts. You should be able to find what you need close by.

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Re: Mechanic can't find a rear end!

Postby kgkoon » Wed Oct 03, 2012 4:48 pm

Thank you. I think I have the 3.73 gears, but is there an easy way to find out?
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Re: Mechanic can't find a rear end!

Postby HenryJ » Wed Oct 03, 2012 5:12 pm

Check out the RPO code list in the glove box. There is a sticky on deciphering it.

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Re: Mechanic can't find a rear end!

Postby LoneWolf04 » Wed Oct 10, 2012 5:13 pm

These rear ends are everywhere... I would start questioning your mechanic. Even if a ZR2 rear end was installed and you do have the 3.73 gearing, there is no reason why it would've went out and he shouldn't be shocked unless if something was seriously out of place. Like he used a drum rear end instead of disc. If you do have the 3.73 and he was trying to match up a 7 5/8" rear end it may be a bit more difficult to locate as most came with the 3.42 gearing. In any case, he shouldn't be afraid of installing a ZR2 rear end in your rig if the gearing is right. You may want to question him some more about what was actualy "wrong" with the install.
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Re: Mechanic can't find a rear end!

Postby mars2878 » Thu Oct 11, 2012 8:52 am

there are no zr5 specific rearends
they are: 2wd w/zq8 w/ 7-5/8 gear
2wd w/o zq8, but w/ & w/o 3rd shock w/ 7-5/8 gear
2wd w/ 8-1/2 gear
4x4 w/ 7-5/8 gear
4x4 w/zr2 w/ 8-1/2 gear
4x4 w/o zr2 w/ 8-1/2 gear

the zr2 rear would give you an additional 2in track width
so as stated before, as long as it was the correct ratio & not drum, then you shouldn't have a problem
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Re: Mechanic can't find a rear end!

Postby kgkoon » Thu Oct 11, 2012 1:35 pm

I'm not sure what is going on. They keep telling me the wrong rear end is being delivered. I do have the 3.73 gears. The last time I talked to them they claimed the ZR2 would cause the wheels to rub because of the additional length and something about a sway bar that doesn't go anywhere on my truck. I'm trying to get them to install the ZR2, but they are hesitant.
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Re: Mechanic can't find a rear end!

Postby HenryJ » Fri Oct 12, 2012 6:10 am

ou use the mounting hardware from your original axle. Sway bar is not used or an issue. Track bar bracket has clearance but is not used. Plenty room for the additional 2" width.Take them the information from my install and pictures. Assure them it is a bolt in swap as long as the u-joint matches.

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Re: Mechanic can't find a rear end!

Postby Lil-j » Tue Oct 23, 2012 2:28 pm

Henry, do have a ink for the install? I'd like to see that.
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Re: Mechanic can't find a rear end!

Postby HenryJ » Tue Oct 23, 2012 2:48 pm

Lil-j wrote:Henry, do have a ink for the install? I'd like to see that.
ZR2 rear axle upgrade.

Image

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
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Re: Mechanic can't find a rear end!

Postby mars2878 » Tue Oct 23, 2012 4:05 pm

Is that a light in the top left of that pic?
01 Sonoma sls crew cab - 00 Camaro rims, lear cap w/additional led int light, reese hitch, 99 envoy dash outlets, 98 bravada switch plates & hvac knobs.
03 grand am se 3.4 auto sedan - 02 gt ram air induction parts, aftmkt taillights.
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Re: Mechanic can't find a rear end!

Postby Jongo88 » Tue Oct 23, 2012 4:57 pm

It looks like the outline of a dead body on the floor....lol
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Re: Mechanic can't find a rear end!

Postby HenryJ » Tue Oct 23, 2012 5:02 pm

mars2878 wrote:Is that a light in the top left of that pic?
Yes. Back up spot light.Yesterdays tech was implement lights. Today's tech is Ozinum LED flood lights. They mount in a 3/8" hole.

Image

My Avalanche has them as puddle lights under the mirrors and corner lights mounted under the rear bumper.
Jongo88 wrote:It looks like the outline of a dead body on the floor....lol
:lol: I never noticed that before. That's the tracks from a Dogbone Roughrider :)

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Re: Mechanic can't find a rear end!

Postby ApproachMedium » Thu Oct 25, 2012 5:34 pm

Nice job! Theres a few guys on the VW forums who have added the same thing with LEDs for puddle lights on their GTis. I want to do them in both my vehicles. Its a nice touch.

How do the corner lights under the rear bumper work? For backing up?
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Re: Mechanic can't find a rear end!

Postby HenryJ » Thu Oct 25, 2012 5:37 pm

ApproachMedium wrote:How do the corner lights under the rear bumper work? For backing up?
Yes. The work great to illuminate the ground behind the truck. Fills that void from the tail lamp lights.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
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Re: Mechanic can't find a rear end!

Postby ApproachMedium » Thu Oct 25, 2012 5:40 pm

Awesome! When I get to replacing my rear bumper I think I will do the same. Sounds like a great idea! I think dads F150 needs this also.
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Re: Mechanic can't find a rear end!

Postby Torskdoc » Wed May 28, 2014 9:13 am

When the Ring Gear bearings finally went in my 95 Jimmy, (3.42) I went down to the local junkyard and got a rear from a 97 Sonoma pickup. Absolutely no problems with installation and the u joint mounts wee the same. I really wanted a rear from a 98 and up Blazer (disc) but most of them had rotted out backing plates, and with no power tools I was using 6ft cheater bar on the shackle nuts. Got it home, installed it with new shackles, brake cylinders, shoes, drums and it runs great. No noise, no clunking. The only downer is the bump stops on the sonoma are different than the Jimmy. (none on the sonoma). So I took bullet shaped stops, fabricated mounts that could be clamped to the axle and went that route with them on top. Works pretty well.
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